This is a proposal to test the feasibility of using triplex molecules for use as a therapeutic to correct Hurler Syndrome (HS). Lysosomal storage diseases (LSDs), such as HS, represent a diverse collection of monogenic disorders that have devastating clinical features. LSDs are caused by mutations in genes that encode lysosomal enzymes and other proteins that are critical for lysosomal function. HS is caused by mutations in the -L-iduronidase gene (IDUA). For many LSDs, treatment consists of enzyme replacement therapy and supportive care. However, enzyme replacement therapy costs from $90,000 to $565,000 per patient. Alternatively, allogeneic hematopoietic stem cell transplantation (HSCT) represents a highly effective treatment. However, allogeneic HSCT requires an HLA-matched donor, is associated with significant morbidity and mortality and is expensive, about $200,000 per patient. Genetic modification of autologous HSCT, using CD34+ cells, is emerging as a viable therapeutic alternative to allogeneic HSCT. Autologous HSCT is preferred because it is far less expensive and safer than allogeneic HSCT. One emerging approach to targeted genome modification in CD34+ cells is the use of triplex molecules, either in the form of triplex-forming oligonucleotides or peptide nucleic acids. These molecules bind to duplex DNA in a sequence-specific manner and stimulate recombination when combined with donor DNA molecules. Gene modification occurs via recruitment of the cells own DNA repair machinery, without the need for viral vectors. Viral vectors have proven problematic in such therapies. Our Specific Aim is to test the feasibility of using triplex molecules to correct one of the most prominent gene mutations in the IDUA gene, W402X. For this technology to be viable as a commercial therapy, we must demonstrate that we can achieve a success rate of at least 3% for correction of our gene target in CD34+ cells. Next, we must demonstrate that we can generate a sufficient number of monocytes from these stem cells to be utilized as part of a bridging therapy to wholesale HSCT. In Phase II, we will carry out in vivo studies to demonstrate in vivo efficacy and work on developmental and IND enabling studies to move this technology toward clinical studies. PUBLIC HEALTH RELEVANCE: Hurler Syndrome (HS), a devastating genetic disease that results in multiple organ failure with progressive deterioration in the central nervous system, is caused by mutations in a single gene that is involved in the processing of large sugar molecules within compartments in our cells. L2 Diagnostics LLC is proposing to develop a therapeutic gene targeting protocol to correct one of the most prominent mutations responsible for HS. Our protocol would repair this mutation in isolated blood stem cells from HS patients and then reintroduce the corrected cells back into the patient with the potential of having a significant impact on the symptoms of the disease.